Before we had autocompletion of categories in the New Story/Media/Template profiles, it used to be that they would remember the last category selected when you go to create a new document. That was lost; so restore it.

Done by adding a new widget, `comp/widgets/profile/autocomplete.mc`, which munges the memorization code from the `select_object` widget with the simple population of a text filed in `text.mc`. Also a callback that handles remembering the value when a form is submitted. That callback, of course, is Bric::App::Callback::Autopopulate.